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July 13, 2012

Milky Way

Another post! Its a miracle!

This photo is of the Milky Way. You can see it stretching gracefully from the bottom right towards the top left.

You might be thinking, wait, are not all the stars in these pictures in the milky way? You would be right, they are all in our galaxy, the milky way. What we are seeing in this picture is the plane of the galaxy.

Our galaxy is a spiral galaxy. One thing that means is that it is flat like a disk. When we see the dust lanes and dense stars like there are in this image, we are looking directly along the plane of the galaxy.

To see this, it needs to be very dark. In Victoria there are not many place to see it, you kinda need to get down to Cattle Point or something very late at night. on a clear day in the summer.

If you can see it, it is spectacular. In the northern hemisphere it is not nearly as dramatic as the southern hemisphere as from the north we can only see out towards the edge of the galaxy rather than in towards the center, but on a good night it is wonderful.

After I wrote this, I sent some of these pictures to my astronomy prof for his viewing pleasure. He saw that I had been looking at Sagittarius, and told me about a nova that had happened a few days ago in Sagittarius. After much searching I have found it in this photo.

Click on the photo to get the larger version. I put two red boxes in the photo. At the very center of the small one is the nova. A small white dot.

The nova is called N 2012 Sag No 4. A nova is a huge explosion on the surface of a star. It is not a supernova when the entire star explodes, but is just on the surface. They happen when a white dwarf star in a binary system has a companion which overflows its Roche lobe. That means that the larger star transfers hydrogen and helium into an accretion disc around the white dwarf. The stuff in the disc falls down onto the white dwarf and piles up. Eventually, if enough stuff lands on it in just the right way, it will flare up, and become very bright for anywhere between 5 and 80 days.

Here is a close up of the area of the large box with the white dot in the center of the small box clearly visible.